Simply vile behaviour from Musk here. Nobody except delusion fanboys would be willing to work for such a company -- maybe that's the point of this cruelty?
This is the point. It's by design. Musk wants that level of loyalty right now. You can hate his methods or decisions, but I think the entire point is he wants 100% dedicated people right now at Twitter.
Given the magnitude of resistance from so much of the staff about the entire acquisition, and the bloat of silicon valley companies on top of it, I can see his reasoning.